Focusing Screens

The focusing screen is a simple device found in the vast majority of professional cameras, and is used to help prepare the photographer in making a shoot. It usually consists of a small lens through which the photographer can peek and estimate what the photo is going to be. The focusing screen often has a set of viewfinder markings on it, similar to a set of crosshairs.

On most professional cameras, the focusing screen is located atop the main body of the camera, often near the shutter button. Advanced cameras will have some other features on display when the user looks into the focusing screen, such as levels measured by a light meter. What the photographer sees via the focusing screen can be thought of as a preview screen for the whole shoot.

Clean Focus Screen

The focusing screen is commonly used to preview the focusing settings of a given photo shoot. The picture that a person sees through the focusing screen will tend to look unfavorable and blurred unless the focusing settings are set right. Professional camera models will also often allow for interchangeable focusing screens that can be swapped in and out to accommodate focusing during low-light settings.

Certain makes of the focusing screen are especially popular devices for astrophotography – photography of celestial bodies. Such focusing screens use a matte surface upon which light from far away can be focused and viewed, and are made to work well for low-light situations.

Canon Focus Screen

Two common forms of the focusing screen are the split-screen and the microprism ring. The split-screen works by showing the image split into two sides of different focusing quality. To focus correctly, the focusing needs to be adjusted so that the two sides are aligned perfectly with one another. The microprism ring works by showing a blurry image until the focus is correct. The microprism ring is the kind that tends to use the viewfinder markings. The split screen does not need to, and is considered the faster method of focusing. The microprism is considered to be somewhat more precise with positioning, owing to the viewfinder markings.

Focus Screens

It is important to keep the focusing screen clean; however, doing so may also entail having to take apart the camera to reach the focusing screen. This must be done carefully, or the screen could get scratched. Some cameras have a function known as autofocus, which performs the job of the focusing screen automatically.